Water-in-oil emulsions containing water-soluble alkyl glycosides

ABSTRACT

A W/O emulsion comprising water, oil and at least one water-soluble alkyl glycoside. Cosmetic and dermatological skincare composition, based thereon are easier to prepare, of lower viscosity and improved stability.

The present invention relates to stable cosmetic compositions, inparticular water-in-oil emulsions (W/O emulsions), which are protectedagainst physical decomposition.

Skincare in the context of the invention is primarily to be understoodas meaning intensifying, assisting and, if necessary, re-establishingthe natural function of the skin as a barrier against environmentalinfluences (for example dirt, foreign substances and microorganisms) andagainst the loss of endogenous substances (for example water,electrolytes and natural moisture-binding substances).

If the natural function of the skin is disturbed, increased absorptionof toxic and/or allergenic foreign substances or attack by pathogenicmicroorganisms and, as a consequence, inflammatory or allergic skinreactions may occur.

The human skin constantly loses a certain amount of moisture byendogenous mechanisms, as it does by transpiration. However, the skinalso loses important functional constituents due to external influences,such as daily washing of the body, wind and weather. Although healthyskin is entirely capable of compensating this loss, the aim of skincareis to assist the skin in compensating this loss. However, precisely whenthe natural regeneration capacity is inadequate, for example due tosevere stress or even an illness, regulation of skin moisture and otherrelevant contents is essential.

The aim of skincare is thus to re-establish and promote a normalfunctional profile of the skin and integumentary appendages.

The following methods of skincare are known per se:

a) Occlusion of the Skin

If the skin is covered with a film of lipid or lipid/water (conventionalointments or creams), the barrier function of the skin is notre-established directly. The lipid film is an external physicalprotective layer.

b) Treatment of the Skin With Essential Fatty Acids

Essential fatty acids are currently occasionally employed indermatological preparations for treatment of dry skin.

c) Treatment of the skin with substances having a keratolytic action(for example urea, salicylic acid and the like). These substances have akeratolytic, proteolytic, penetration-promoting, epidermis-thinning,antipruritic or water-binding action, depending on their nature and theconcentration used. Their use is essentially limited to medicalindications.

d) Treatment with moisture-regulating substances (for example glycerol,sorbitol and the like). The group of these substances is of particularinterest, since it includes many representatives which have a goodaction. Nevertheless, a disadvantage is that most of these substanceseither are expensive or can be incorporated into cosmetic formulationsonly under complicated conditions. The statements under point c)furthermore apply to some representatives of this group.

Skincare cosmetic formulations include, in particular, cosmeticemulsions, that is to say W/O emulsions.

Emulsions of this type can on the one hand be employed without an activecompound, a good action in general already being achieved, but on theother hand emulsions containing active compounds are being used more andmore. It was thus an object of the present invention to provide W/Oemulsions which both can function as a vehicle for active compounds ofthe most diverse types and also have outstanding dermatologicalproperties without an active compound.

A disadvantage of many water-in-oil emulsions of the prior art isfurthermore that they are not stable towards physical decomposition. Theundesirable behaviour which occurs the most frequently is usually called"oiling out". This means that the aqueous phase and oily phase graduallyseparate. This manifests itself, for example, in drops of oil emergingfrom a W/O cream (=water-in-oil cream). However, once an emulsion hasstarted to decompose, this process cannot be reversed again by simplemeans. At least, such means are not available to the user.

W/O emulsions are particularly sensitive towards a content of highlysurface-active substances, the water-solubility of which is high, incontrast to emulsifiers, the fat-solubility of which is high.

W/O emulsions have hitherto always been destroyed by addition of highlysurface-active substances of the prior art, this having manifesteditself in phase separation.

The object of the present invention was thus to eliminate all thedisadvantages of the prior art. In particular, stable skincare W/Oemulsions were to be provided.

It has been found, surprisingly, and therein lies the achievement of theobject, that W/O emulsions comprising a water-soluble alkyl glycoside ora mixture of several water-soluble alkyl glycosides remedy thedisadvantages of the prior art.

The alkyl glycosides according to the invention are distinguished by thestructure

    Glyc--O--R

in which R, the aglycon, is a branched or unbranched alkyl radicalhaving 5-18 carbon atoms, preferably an unbranched alkyl radical having8-10 carbon atoms.

According to the invention, Glyc is a monosaccharidic sugar residuewhich is linked glycosidically with the aglycon R.

Advantageous embodiments of the present invention exist if Glyc ischosen from the group consisting of hexosyl residues, that is to say,for example, glucosyl, mannosyl, galactosyl and fructosyl.

It is essential to the invention in all cases that the alkyl glycosideschosen are readily water-soluble.

Preferred embodiments of the present invention are W/O emulsionscomprising an alkyl glucosides or a mixture of several alkyl glucosides,that is to say those glycosides in which Glyc is a glucosyl radical.

Alkyl glucosides are distinguished by the structure ##STR1## R is abranched or unbranched alkyl radical having 5-14 carbon atoms,preferably an unbranched alkyl radical having 8-10 carbon atoms.

Although the alkyl glucosides according to the invention canadvantageously be chosen per se both from α-D-glucosides and fromβ-D-glucosides, the β-D-glucosides (or their mirror image forms, whichare, however, less readily accessible) are preferred. This is based onthe fact that the α-D-glucosides in general have a poorerwater-solubility than the β-D-glucosides.

The alkyl glucosides are particularly advantageously distinguished bythe following structures: ##STR2##

The emulsions according to the invention preferably comprise up to 0.5%by weight of alkyl glycosides, advantageously alkyl glucosides,preferably up to 0.3% by weight, in each case based on the total weightof the W/O emulsion. Concentrations of 0.001 to 0.20% by weight, basedon the total weight of the W/O emulsion, are especially preferablyemployed.

In particular, it is also advantageous to chose the concentration of thealkyl glycosides according to the invention such that it is smaller thanthe particular critical micelle formation concentration (CMC).

Since alkyl glycosides belong to the highly surface-active substances,it was astonishing that an addition of alkyl glycosides to W/O emulsions

would be stable,

would lead to emulsions which, cosmetically, are of particularly highquality,

would lead to particularly smooth emulsions,

would lead to emulsions having a particularly pronounced skincareaction,

would lead to vehicles for many types of active compounds.

The W/O emulsions according to the invention obligatorily comprise a W/Oemulsifier or an emulsifier mixture which would also lead to W/Oemulsions without addition of the alkyl glycosides according to theinvention.

Without alkyl glycosides, however, W/O emulsions are obtained which havea lower stability, have a cosmetic elegance which leaves something to bedesired, which are more viscous than smooth and which have a lesspronounced skincare action. Furthermore, such W/O emulsions are lesssuitable as a vehicle for active compounds.

The alkyl glycosides thus improve the properties of the W/O emulsion,hut are themselves not W/O emulsifiers.

It was furthermore astonishing that a significantly improved start ofthe emulsion formation is to be observed by using the alkyl glycosidesaccording to the invention. This is to be understood as meaningimmediate formation of an emulsion after the corresponding fatty andaqueous phases have been brought together.

Furthermore, compared with batches without the alkyl glycosidesaccording to the invention, the viscosity of the resulting W/O emulsionsis significantly reduced, the consistency is noticeably improved and thetendency of the emulsion to oil out, that is to say to separate into anaqueous and an oily phase, is considerably reduced.

It is of course known to the expert that high-quality cosmeticcompositions are usually inconceivable without the customary auxiliariesand additives. These include, for example, consistency agents, fillers,perfume, dyestuffs, emulsifiers, additional active compounds such asvitamins or proteins, light protection agents, stabilizers,antioxidants, insect repellents, alcohol, water, salts, antimicrobial,proteolytic or keratolytic substances and the like.

Depending on their build-up, the compositions according to the inventioncan accordingly be used, for example, as skin protection cream,cleansing milk, sunscreen lotion, nutrient cream, day or night cream andthe like. Where appropriate, it is possible and advantageous to use thecompositions according to the invention as a base for pharmaceuticalformulations.

The invention also relates to the use of the W/O emulsions described ascosmetic and/or dermatological skincare compositions. The W/O emulsionsaccording to the invention are advantageously prepared by introducingthe alkyl glycoside or alkyl glycosides and the other water-solublecomponents into the aqueous phase, introducing the oil-solublecomponents into the fatty phase and combining and then homogenizing theaqueous phase and the oily phase with one another at a temperature atwhich both phases are in the liquid form.

The invention thus also relates to a process for the preparation of theW/O emulsions described, characterized in that the water-soluble alkylglycoside or water-soluble alkyl glucosides and the other water-solublecomponents are introduced into the aqueous phase, the oil-solublecomponents are introduced into the fatty phase and the aqueous phase andthe oily phase are combined and then homogenized with one another at atemperature at which both phases are in the liquid form.

However, it is particularly advantageous to carry out processes for thepreparation of W/O emulsions according to the invention which proceed inaccordance with the hot/cold technique. This means that one of thephases to be combined (preferably the aqueous phase) is at roomtemperature, while the other phase (preferably the fatty phase) is athigher temperatures, in particular at temperatures at which all thesolid constituents of the phase in question are in liquid or dissolvedform.

The invention therefore preferably relates to a process for thepreparation of W/O emulsions according to the invention, characterizedin that the water-soluble alkyl glycoside or the water-soluble alkylglucosides and the other water-soluble components are introduced intothe aqueous phase, the oil-soluble components are introduced into thefatty phase, the aqueous phase being at a temperature of between 15° and35° C. and the oil phase being at a temperature at which all the solidconstituents of the oily phase are in liquid or dissolved form, and theaqueous phase and the oily phase are combined with one another and thenhomogenized.

The advantage of this particularly preferred preparation process isthat, because one phase can be essentially at room temperature,considerable amounts of energy can be saved during the preparation.

The following examples are intended to illustrate the invention in moredetail, but without the intention of limiting the invention to theseexamples. Rather, on the basis of his or her expert knowledge, theexpert is capable of making modifications which do not go beyond thescope of the present invention.

The amounts data in the examples relate to % by weight, based on thetotal composition.

EXAMPLE 1

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polyglyceryl 3-diisostearate                                                                       2.50                                                     Paraffin wax         3.00                                                     Paraffin oil DAB 9   10.00                                                    Cetearyl octanoate   10.00                                                    Beeswax              4.00                                                     Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.01                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 2

    ______________________________________                                                             % by weight                                              ______________________________________                                        Cholesterol          1.50                                                     Paraffin wax         3.00                                                     Vaseline             5.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             .5.00                                                    Decyl β-D-glucoside                                                                           0.01                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 3

    ______________________________________                                                             % by weight                                              ______________________________________                                        Wool wax alcohols    2.50                                                     Paraffin wax         6.00                                                     Beeswax              1.00                                                     Vaseline             3.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.01                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 4

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polyglyceryl 3-diisostearate                                                                       2.50                                                     Paraffin wax         3.00                                                     Paraffin oil DAB 9   10.00                                                    Cetearyloctanoate    10.00                                                    Beeswax              4.00                                                     Glycerol             5.00                                                     Octyl β-D-glucoside                                                                           0.05                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 5

    ______________________________________                                                             % by weight                                              ______________________________________                                        Cholesterol          1.50                                                     Paraffin wax         3.00                                                     Vaseline             5.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             5.00                                                     Octyl β-D-glucoside                                                                           0.05                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 6

    ______________________________________                                                             % by weight                                              ______________________________________                                        Wool wax alcohols    2.50                                                     Paraffin wax         6.00                                                     Beeswax              1.00                                                     Vaseline             3.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.05                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 7

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polyglyceryl 3-diisostearate                                                                       1.50                                                     PEG 40 sorbitan heptaisostearate                                                                   1.50                                                     Paraffin oil DAB 9   15.00                                                    Vaseline             8.00                                                     Paraffin wax         6.00                                                     2-Octyldodecanol     8.00                                                     Aluminium stearate   0.20                                                     Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.01                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 8

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polyglyercyl 3-diisostearate                                                                       1.50                                                     PEG 40 sorbitan heptaisostearate                                                                   1.50                                                     Paraffin oil DAB 9   15.00                                                    Vaseline             8.00                                                     Paraffin wax         6.00                                                     2-Octyldodecanol     8.00                                                     Aluminium stearate   0.20                                                     Glycerol             5.00                                                     Octyl β-D-glucoside                                                                           0.05                                                     Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 9

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polyglyceryl 3-diisostearate                                                                       2.50                                                     Paraffin wax         3.00                                                     Paraffin oil DAB 9   10.00                                                    Cetearyl octanoate   10.00                                                    Beeswax              4.00                                                     Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.003                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 10

    ______________________________________                                                             % by weight                                              ______________________________________                                        Cholesterol          1.50                                                     Paraffin wax         3.00                                                     Vaseline             5.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.003                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 11

    ______________________________________                                                             % by weight                                              ______________________________________                                        Wool wax alcohols    2.50                                                     Paraffin wax         6.00                                                     Beeswax              1.00                                                     Vaseline             3.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.003                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 12

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polyglyceryl 3-diisostearate                                                                       2.50                                                     Paraffin wax         3.00                                                     Paraffin oil DAB 9   10.00                                                    Cetearyl octanoate   10.00                                                    Beeswax              4.00                                                     Glycerol             5.00                                                     Octyl β-D-glucoside                                                                           0.005                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 13

    ______________________________________                                                             % by weight                                              ______________________________________                                        Cholesterol          1.50                                                     Paraffin wax         3.00                                                     Vaseline             5.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             5.00                                                     Octyl β-D-glucoside                                                                           0.005                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 14

    ______________________________________                                                             % by weight                                              ______________________________________                                        Wool wax alcohols    2.50                                                     Paraffin wax         6.00                                                     Beeswax              1.00                                                     Vaseline             3.00                                                     Paraffin oil DAB 9   20.00                                                    Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.003                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 15

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polygylceryl 3-diisostearate                                                                       1.50                                                     PEG-40 sorbitan heptaisostearate                                                                   1.50                                                     Paraffin oil DAB 9   15.00                                                    Vaseline             8.00                                                     Paraffin wax         6.00                                                     2-Octyldodecanol     8.00                                                     Aluminium stearate   0.20                                                     Glycerol             5.00                                                     Decyl β-D-glucoside                                                                           0.003                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

EXAMPLE 16

    ______________________________________                                                             % by weight                                              ______________________________________                                        Polyglyceryl 3-diisostearate                                                                       1.50                                                     PEG-40 sorbitan heptaisostearate                                                                   1.50                                                     Paraffin oil DAB 9   15.00                                                    Vaseline             8.00                                                     Paraffin wax         6.00                                                     2-Octyldodecanol     8.00                                                     Aluminium stearate   0.20                                                     Glycerol             5.00                                                     Octyl-β-D-glucoside                                                                           0.005                                                    Perfume, preservative, additives                                                                   q.s.                                                     Water                to 100.00                                                ______________________________________                                    

COMPARISON EXPERIMENT 1

A W/O emulsion was prepared with the composition according to Example 11by bringing together fatty phase: of wool wax alcohols, paraffin wax,beeswax, vaseline and paraffin oil DAB 9, temperature: 75° C. aqueousphase: glycerol, decyl β-D-glucoside, water (without perfume,preservative, additives), temperature: 75° C.

A smooth emulsion was formed immediately.

COMPARISON EXPERIMENT 2

A W/O emulsion according to Comparison Experiment 1 was prepared, withthe only difference that no decyl β-glucoside was added. It took tenminutes for a viscous emulsion to be formed.

COMPARISON EXPERIMENT 3

A W/O emulsion was prepared with the composition according to Example11, by bringing together fatty phase: of wool wax alcohols, paraffinwax, beeswax, vaseline and paraffin oil DAB 9, temperature: 75° C.aqueous phase: glycerol, decyl β-D-glucoside, water (without perfume,preservative, additives), temperature: 25° C.

A smooth emulsion was formed practically immediately.

COMPARISON EXPERIMENT 4

A W/O emulsion according to Comparison Experiment 3 was prepared, withthe only difference that no decyl β-glucoside was added. It took abouttwenty minutes for an emulsion which was unstable and cosmeticallyunacceptable to be formed.

We claim:
 1. A water-in-oil emulsion comprising water, oil and 0.001 to0.20% by weight of a water-soluble alkyl glycoside or of a mixture ofwater-soluble alkyl glycosides.
 2. A water-in-oil emulsion according toclaim 1, wherein the water-soluble alkyl glycoside is an alkylglucoside.
 3. A water-in-oil emulsion according to claim 1, wherein thealkyl glucoside is at least one of ##STR3## wherein R is a branched orunbranched alkyl radical having 5-18 carbon atoms.
 4. A water-in-oilemulsion according to claim 3, wherein the alkyl glucoside is ofβ-configuration and R is an unbranched alkyl radical of 8-10 carbonatoms.
 5. A water-in-oil emulsion according to claim 1, wherein thealkyl glucoside is ##STR4##
 6. A water-in-oil emulsion according toclaim 1, wherein the alkyl glycoside is present in 0.3 to 0.5% based onthe total weight of the W/O emulsion.
 7. A water-in-oil emulsionaccording to claim 1, containing a cosmetic or dermatological skincareingredient.
 8. A low-viscosity water-in-oil emulsion according to claim5, wherein the alkyl glycoside is present in 0.3 to 0.5% and aconcentration of alkyl glycosides, in each case based on the totalweight of the W/O emulsion, the emulsion further containing a cosmeticor dermatological skincare ingredient.
 9. A process for the preparationof a water-in-oil emulsion according to claim 1, comprising introducingthe water-soluble alkyl glycoside and any other water-soluble componentsinto water to form an aqueous phase, combining oil-soluble components toform a fatty phase, combining the aqueous phase and the oily phase withone another, and homogenizing the mixture at a temperature at which bothphases are in liquid form.
 10. A process according to claim 9, wherein,when mixed, the water aqueous phase is at a temperature of between 15°and 35° C. and the oil phase is at a temperature at which all the solidconstituents of the oily phase are in liquid or dissolved form.